New to gardening and totally lost!!!

HELP!!! Yes, I am new to this site, and also new to gardening. My name is Denel, I am 50 years old, I live in Alabama, and I have no idea how to garden. I mean, the sum of my experience is helping friends weed and water when I lived with them, helping my stepmom plant a few flowers, attempting to grow one plant of tomatoes (epic fail), and a couple of potted flowers. One pot I think flourished in spite of me. The other...well, there was a funeral and tears involved...lol.
Oh man! What was I thinking?!? But I have to do it. I have to completely change my diet due to some health issues. I can explain that more later. But have you seen grocery prices for healthy food? Yeah! Without me being able to work, there's no way I can afford to double or triple our family food budget! So, I have donned an apron and pot holders, and gardening gloves and a spade!
OK...I may be an idiot, but I'm not stupid! lol I figured I would just go pick up some plants and some seeds, read the "instructions" and be good to go. Not so much! There are terms like "Size: 2 year" "Harvest: Mid Season", etc. What the heck?!?
Not to mention, I guess I can't just go dig a hole and put my plant in it. There's manure, top soils, and a few other things. Mulch until threat of frost is over. What? I'm pretty sure threat of frost is over...I live in Alabama. But the only mulch I know anything about is the stuff my dad put in the space around the house to keep weeds out and make the lawn look more manicured...40 years ago! I'm pretty sure you don't want to put that stuff around your veggies or herbs.
Also, some of my plants say full-sun, some say partial-sun. OK, full-sun is easy to figure out...but how much time do they need to get full-sun? I have lots of trees, so it's hard to find a good area that gets more than a couple of hours. And with the ones that say partial-sun...do I have to have 2 separate garden areas?
Can you see I have NO idea what the heck I am doing? In all of my veggie and herb purchases, I did buy myself a nice rose bush. I figured that would be easy enough...just plant it next to my steps. Even that was a head-scratcher. You have to dig so deep, with the hole being so big around...ok, got it. But then it was talking about covering the plant to about 2 inches from the bud union. What the heck is a bud union?
Oh gosh...this has become a book...and I have so many more questions. So glad I found this site. Hopefully I don't kill everything before I learn some stuff. I have 12 plants to transplant, and about 25 seeds to plant. Man, what was I thinking?!? Hopefully y'all can help me out.